"The ratio is 2:3. The flag is divided by lozengy into blue and yellow and in each of the blue lozenges is one yellow inescutcheon. In the centre is the municipal coat of arms."

For me the official description doesn't match the image. Suggestion:
It is a yellow flag with six blue lozenges ordered two times three with a yellow inescutcheon in every lozenge. In the centre of the flag is the municipal coat of arms: shield divided per fess into blue and red. In the centre is a golden (yellow) castle, masoned black, having three golden turrets with pinnacles and a blue open gate and windows of the same colour.

If the flag would be divided by lozengy, for me the lozenges should have touched the edges of flag.